Surface mount crystal oscillator and manufacturing method of the same

A surface mount crystal oscillator comprising a crystal piece held by first and second crystal holding terminals on a rectangular ceramic substrate, and sealed with a metal cover via a seal material of a molten resin,

• wherein one leading electrode and the other leading electrode of the crystal piece are led in the same direction,
• the first crystal holding terminal and the second crystal holding terminal constitute such a cantilever type as to hold one end of the crystal piece,
• on wall faces of through holes formed in corner portions of the substrate, through terminals are formed,
• on the front surface of the substrate, a first leading terminal led from the first crystal holding terminal is connected to the through terminal of the shortest corner portion, and a second leading terminal led from the second crystal holding terminal is connected to the through terminal of the corner portion in a direction reverse to a direction in which the first leading terminal is led, on the back surface of the substrate, mount terminals connected to the through terminals are formed,
• the first crystal holding terminal is connected to the one leading electrode led to one side of the crystal piece by a conductive adhesive in an end portion from which the first leading terminal is led,
• the second crystal holding terminal is connected to the other leading electrode led to the one side of the crystal piece by a conductive adhesive in the one side of the crystal piece from which the other leading electrode is led, and the second leading terminal passes under the crystal piece from a position of the second crystal holding terminal connected by the conductive adhesive and is connected to the through terminal of the corner portion in the direction reverse to the direction in which the first leading terminal is led, and
• the opening end face of the metal cover joined onto the ceramic substrate via the molten resin comprises a flange having an inclined face.

A manufacturing method of a surface mount crystal oscillator comprising a crystal piece held by first and second crystal holding terminals on a rectangular ceramic substrate, and sealed with a metal cover via a seal material of a molten resin, comprising:

• a step of forming, in a sheet-like ceramic material, break lines which specify individual ceramic substrate regions and through holes which correspond to corner portions of the regions and firing the ceramic material to form a sheet-like ceramic base;
• a step of forming metal layers of through terminals on wall faces of the through holes, forming, on the front surface of the ceramic base, a pattern of a metal layer in which the first crystal holding terminal and a first leading terminal led from the terminal are connected to the through terminal of the shortest corner portion, and a second leading terminal led from the second crystal holding terminal is connected to the through terminal of the corner portion in a direction reverse to a direction in which the first leading terminal is led, and forming, on the back surface of the ceramic base, a pattern of a metal layer of mount terminals connected to the through terminals;
• a step of mounting the crystal piece on the first and second crystal holding terminals;
• a step of regulating a vibration frequency by use of the mount terminal connected to the first crystal holding terminal and the mount terminal connected to the second crystal holding terminal;
• and
• a step of immersing, into a molten resin solution, a flange having an inclined face as the opening end face of the metal cover joined onto the ceramic substrate via the molten resin to form a reservoir portion of the molten resin on the lower surface of the flange, and securing the flange onto the ceramic substrate in a state in which the reservoir portion is formed.